NCERT Solutions for Class 11 Science Biology Chapter 12 Mineral Nutrition are provided here with simple step-by-step explanations. These solutions for Mineral Nutrition are extremely popular among Class 11 Science students for Biology Mineral Nutrition Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the NCERT Book of Class 11 Science Biology Chapter 12 are provided here for you for free. You will also love the ad-free experience on Meritnation’s NCERT Solutions. All NCERT Solutions for class Class 11 Science Biology are prepared by experts and are 100% accurate.
Page No 63:
Question 1:
Which one of the following roles is not characteristic of an essential element?
a. being a component of bio-molecules
b. changing the chemistry of soil
c. being a structural component of energy related chemical compounds
d. activation or inhibition of enzymes
Answer:
Essential elements play an important role in controlling several metabolic processes in the plant cell. For example - cell membrane permeability, involved in the maintenance of osmotic concentration of cell sap, electron-transport systems, buffering action, controls several enzymatic activities and acts as an important constituent of macromolecules and coenzymes. Thus, changing the chemistry of soil is not the role of essential elements.
Hence, the correct answer is option b.
Page No 63:
Question 2:
Which one of the following statements can best explain the term critical concentration of an essential element?
a. essential element concentration below which plant growth is retarded.
b. essential element concentration below which plant growth becomes stunted.
c. essential element concentration above which plant remains in the vegetative phase.
d. none of the above
Answer:
Critical concentration is the concentration of the essential element below which plant growth is retarded. Plants show deficiency symptoms below the critical concentration of a particular element.
Hence, the correct answer is option a.
Page No 63:
Question 3:
Deficiency symptoms of an element tend to appear first in young leaves. It indicates that the element is relatively immobile. Which one of the following elemental deficiency would show such symptoms?
a. sulphur
b. magnesium
c. nitrogen
d. potassium
Answer:
The elemental deficiency of sulphur causes premature fall of leaves and indicates that sulphur is relatively immobile.
Hence, the correct answer is option a.
Page No 63:
Question 4:
Which one of the following symptoms is not due to manganese toxicity in plants?
a. Calcium translocation in shoot apex is inhibited
b. Deficiency in both Iron and Nitrogen is induced
c. Appearance of brown spot surrounded by chlorotic veins
d. None of the above
Answer:
The symptoms of manganese toxicity are:
(i) Appearance of brown sports that surrounds the chlorotic veins.
(ii) Inhibition of calcium translocation in shoot apex.
(iii) Excessive concentration of manganese also induces the deficiencies of iron, magnesium and calcium.
Hence, the correct answer is option b.
Page No 64:
Question 5:
Reaction carried out by N2 fixing microbes include
Which of the following statements about these equations is not true
a. step (i) is carried out by Nitrosomonas or Nitrococcus
b. step (ii) is carried out by Nitrobacter
c. both steps (i) and (ii) can be called nitrification
d. bacteria carrying out these steps are usually photoautotrophs
Answer:
In the given chemical equation, Ammonia is first oxidised by the bacteria Nitrosomonas or Nitrococcus into nitrite and is further oxidised. These steps are nitrification and nitrifying bacteria are chemoautotrophs.
Hence, the correct answer is option d.
Page No 64:
Question 6:
With regard to the Biological Nitrogen Fixation by Rhizobium in association with soybean, which one of the following statement/statements does not hold true.
a. Nitrogenase may require oxygen for its functioning.
b. Nitrogenase is MO- Fe protein
c. Leg-hemoglobin is a pink coloured pigment.
d. Nitrogenase helps to convert N2 gas into two molecules of ammonia.
Answer:
Nitrogenase enzyme is highly sensitive to the molecular oxygen and requires anaerobic condition for its proper functioning. So, the root nodules have some adaptations to protect the enzyme from oxygen, For this purpose, root nodules contains an oxygen-scavenger called leg haemoglobin.
Hence, the correct answer is option a.
Page No 64:
Question 7:
Match the element with its associated functions / roles and choose the correct option among given below.
| A. Boron | i. splitting of H2O to liberate O2 during photosynthesis |
| B. Manganese | ii. needed for synthesis of auxins |
| C. Molybdenum | iii. component of nitrogenase |
| D. Zinc | iv. Pollen germination |
| E. Iron | v. component of ferredoxin |
a. A-i, B-ii, C-iii, D-iv, E-v
b. A-iv, B-i, C-iii, D-ii, E-v
c. A-iii, B-ii, C-iv, D-v, E-i
d. A-ii, B-iii, C-v, D-i, E-iv
Answer:
Correct Match:
​
| A. Boron | iv. Pollen germination |
| B. Manganese | i. splitting of H2O to liberate O2 during photosynthesis |
| C. Molybdenum | iii. component of nitrogenase |
| D. Zinc | ii. needed for synthesis of auxins |
| E. Iron | v. component of ferredoxin |
Hence, the correct answer is option c.
Page No 64:
Question 8:
Plants can be grown in (Tick the incorrect option)
a. soil with essential nutrients.
b. water with essential nutrients.
c. either water or soil with essential nutrients.
d. water or soil without essential nutrients.
Answer:
Plants can be grown in soil and water with essential nutrient. Soil deficient in nutrients do not support the growth of plants.
Hence, the correct answer is option d.
Disclaimer: The answer given in NCERT exemplar is incorrect as plants cannot grow without essential nutrients. Thus, the correct answer is option d.
Page No 65:
Question 1:
Name a plant, which accumulate silicon.
Answer:
Oryza sativa and Triticum aestivum are some plants that accumulate silicon. It is actively absorbed and accumulated in their biomass.
Page No 65:
Question 2:
Mycorrhiza is a mutualistic association. How do the organisms involved in this association benefit from each other?
Answer:
Fungi form symbiotic association with plants called mycorrhiza. In this mutual association, the fungi gets shelter and food from plants and in turn they absorb water and phosphorus from soil and passes it to the plant.
Page No 65:
Question 3:
Nitrogen fixation is shown by prokaryotes and not by eukaryotes. Comment.
Answer:
Nitrogenase enzyme is required for the process of nitrogen fixation and is only present in prokaryotes sucha as Rhizobium and Anabaena. This is the reason that nitrogen fixation is shown by prokaryotes and not by eukaryotes.
Page No 65:
Question 4:
Carnivorous plants like Nepenthes and Venus fly trap have nutritional adaptations. Which nutrient do they especially obtain and from where?
Answer:
Nepenthes and venus - fly trap are carnivorous plant that grow in soil which is deficient in nitrogen. These plants constitute their nitrogen deficiency by trapping insects and for this reason they have developed special adaptations.
Page No 65:
Question 5:
Name a plant which lacks chlorophyll. How will it obtain nutrition?
Answer:
A plant which lacks chlorophyll is Cuscuta (amarbel) and this plant lives as a parasite on other plants to derive their nutrition.
Page No 65:
Question 6:
Name an insectivorous angiosperm.
Answer:
Bladderwort or Utricularia is an insectivorous angiosperm.
Page No 65:
Question 7:
A farmer adds Azotobacter culture to soil before sowing maize. Which mineral element is being replenished?
Answer:
Azotobacter and Beijerinckia are free-living nitrogen-fixing aerobic microbes. Azotobacter culture is introduced by the farmer in soil before sowing maize as it will replenish the nitrogen content of the soil by the process of nitrogen fixation.
Page No 65:
Question 8:
What is the function of leghaemoglobin in the root nodule of a legume?
Answer:
Leg haemoglobin is a red-coloured iron - containing pigment present in the root nodules of leguminous plants (soyabean). For example - It acts as an oxygen scavenger molecule. This pigment protects the nitrogenase enzyme to bind with oxygen and helps in proper functioning of the enzyme, thus converting atmospheric nitrogen to ammonia (NH3).
Page No 65:
Question 9:
What is common to Nepenthes, Utricularia and Drosera with regard to mode of nutrition?
Answer:
Nepenthes, Utricularia and Drosera are insectivorous plants that trap insects and feed them to get nutrition.
Page No 65:
Question 10:
Plants with zinc deficiency show reduced biosynthesis of _______________.
Answer:
Zinc is an essential nutrient element for plants and they obtain zinc in the form of Zn2+ ions. It is required for the synthesis of auxin. Deficiency of zinc in plant show reduced biosynthesis of auxin.
Page No 65:
Question 11:
Yellowish edges appear in leaves deficient in ______________ mineral.
Answer:
Yellowish edges appear in leaves deficient in nitrogen, magnesium, potassium and iron.
Page No 65:
Question 12:
Name the macro-nutrient which is a component of all organic compounds but is not obtained from soil.
Answer:
Carbon is a macronutrient that is used as a major component of all organic compound and is not obtained from the soil. It is obtained from atmosphere in the form of CO2.
Page No 65:
Question 13:
Name one non-symbiotic nitrogen fixing prokaryote.
Answer:
Azotobacter and Beijerinckia are non-symbiotic free-living nitrogen fixing bacteria.
Page No 65:
Question 14:
Rice fields produce an important greenhouse gas. Name it.
Answer:
CH4 or methane gas is an important greenhouse gas produced in the rice field due to microbial activity.
Page No 65:
Question 15:
Complete the equation for reductive amination ?
Answer:
Page No 65:
Question 16:
Excess of Mn in soil leads to defeciency of Ca, Mg and Fe. Explain.
Answer:
Manganese is a micronutrient and its moderate increase in the concentration results in toxicity. This micronutrient competes with iron and magnesium for their uptake. It competes with magnesium for binding with enzymes. It also inhibit calcium translocation in shoot apex. Higher concentration of manganese cause deficiencies of iron, magnesium and calcium.
Page No 65:
Question 1:
How is sulphur important for plants? Name the aminoacids in which it is present.
Answer:
Sulphur is present in two amino acids - cysteine and methionine. It is the important constituent of several coenzymes, vitamins such as thiamine, biotin, coenzyme A and ferredoxin. It is used in growth metabolism, nodule formation, chlorophyll formation. Plants obtain sulphur in the form of sulphate
Page No 66:
Question 2:
How are organisms like Pseudomonas and Thiobacillus of great significance in nitrogen cycle?
Answer:
Pseudomonas and Thiobacillus are denitrifying bacteria that carry out the process of denitrification. In this process, nitrate (NO3-) and nitrite (NO2-) present in the soil is reduced to free nitrogen (N2) under anaerobic conditions. Thus, nitrogen is released and returned back into the atmosphere.
Page No 66:
Question 3:
Carefully observe the following figure
a. Name the technique shown in the figure and the scientist who demonstrated this technique for the first time.
b. Name atleast three plants for which this technique can be employed for their commercial production.
c. What is the significance of aerating tube and feeding funnel in this setup?
Answer:
a. The given-technique is called hydroponics. It is the technique of growing plants in a nutrient medium. Julius Von Sachs, a german botonist in 1860 demonstrated this technique for the first time.
b. Hydroponics is successfully used for the commercial production of vegetables like tomato, seedless cucumber and lettuce.
c. Feeding funnel is used for the addition of water and mineral in the hydroponic system. Aerating tube is used to provide sufficient amount of oxygen for normal growth and development of roots.
Page No 66:
Question 4:
Name the most crucial enzyme found in root nodules for N2 fixation? Does it require a special pink coloured pigment for its functioning? Elaborate.
Answer:
Nitrogenase enzyme and leghaemoglobin are the biochemical components present in the root nodules of leguminous plant. Nitrogenase enzyme is a Mo-Fe protein that catalyses the conversion of atmosphere nitrogen into ammonia. Ammonia is the first stable product of nitrogen fixation. This enzyme is highly sensitive to molecular oxygen and requires anaerobic condition for function. Leghaemoglobin is a red colour iron containing pigment and is an oxygen scavenger that protects the enzyme.
Page No 66:
Question 5:
How are the terms ‘critical concentration’ and ‘deficient’ different from each other in terms of concentration of an essential element in plants? How will you find the values of ‘critical concentration’ and ‘deficient’ for minerals – Fe & Zn?
Answer:
Critical concentration is the concentration of the essential element below which plant growth is retarded.
An element is said to be deficient when it is present below its critical concentration that retard the plant growth.
| Element | Critical concentration | Deficient |
| Fe | 3.5 - 5% | < 3.5% |
| Zn | 0.5 - 1% | < 0.5% |
Page No 66:
Question 6:
Carnivorous plants exhibit nutritional adaptation. Citing an example explain this fact.
Answer:
Venus flytrap and pitcher plant are insectivorous plants. Such plants grow in marshy and swamp areas. They grow in nitrogen deficient soil and to fulfil their nitrogen requirements, these plants feed on insects. They show several adaptions to trap insects. As, the leaf lamina of the pitcher plant is modified into a pitcher along with a lid. Digestive enzymes are present in the inner wall of the pitcher plant to digest and absorb nitrogenous nutrients from the insects.
Page No 66:
Question 7:
A farmer adds / supplies Na, Ca, Mg and Fe regularly to his field and yet he observes that the plants show deficiency of Ca, Mg and Fe. Give a valid reason and suggest a way to help the farmer improve the growth of plants.
Answer:
Micronutrients are required by plants in very low/trace amounts. A slight decrease in their amount than moderate causes the deficiency symptoms while concentration above moderate causes toxicity. Farmers use broad-spectrum fertilizers that contain manganese. Manganese competes with iron and magnesium for uptake. It competes with magnesium for binding with enzymes. It also inhibits translocation of calcium in shoot apex. Balance the use of broad-spectrum fertilizer in order to avoid manganese toxicity. Application of lime is done on acidic soil to reduce the concentration of manganese.
Page No 67:
Question 1:
It is observed that deficiency of a particular element showed its symptoms initially in older leaves and then in younger leaves.
a. Does it indicate that the element is actively mobilized or relatively immobile?
b. Name two elements which are highly mobile and two which are relatively immobile.
c. How is the aspect of mobility of elements important to horticulture and agriculture?
Answer:
a. The elements that are actively mobilized show deficiency symptoms in older leaves first. This indicates that the element is mobilised actively. In the older leaves, elements of a particular nutrient are broken down and then mobilised to younger leaves. But for elements that are immobile, deficiency might appear first in younger leaves.
b. Highly mobilised element: Magnesium (Mg) and nitrogen (N)
Relatively immobile element: Calcium (Ca) and sulphur (S)
c. The aspect of mobility of elements is very important for horticulture and agriculture as observing the cause of deficiency symptoms in older or younger parts of the leaves, helps the farmer to analyse whether the deficiency is caused due to highly mobilised element or by relatively immoblised element. It also helps the farmer to treat the plants on the basis of this observation.
Page No 67:
Question 2:
We find that Rhizobium forms nodules on the roots of leguminous plants. Also Frankia another microbe forms nitrogen fixing nodules on the roots of non-leguminous plant Alnus.
a. Can we artificially induce the property of nitrogen fixation in a plant – leguminous or non-leguminous?
b. What kind of relationship is observed between mycorrhiza and pine trees?
c. Is it necessary for a microbe to be in close association with a plant to provide mineral nutrition? Explain with the help of one example.
Answer:
(a) The success rate for artificial induction of nitrogen fixation is very low because expression of gene is highly specific phenomenon. This method of artificial induction of nitrogen fixation in leguminous and non-leguminous plants have been tried by scientist many times.
(b). A symbiotic (mutulism) relationship is found between the pine roots and mycorrhiza. Both provides benefits to each other.
(c). Yes, it is necessary for a microbe to be in close association with a plant to provide mineral nutrient.
For example- Rhizobium lives in the root nodules of leguminous plant and incorporated into the root tissues and this only helps to carry out the process of nitrogen fixation .
Page No 67:
Question 3:
What are essential elements for plants? Give the criteria of essentiality? How are minerals classified depending upon the amount in which they are needed by the plants?
Answer:
An element is said to be essential when required by the plants for its normal growth and development. This requirement of these elements must be specific and are not replaced by another elements in the soil.
They are divided into two categories:-
(1) Macronutrients: These elements are present in plant tissues in large amount. For example:- carbon, hydrogen, oxygen, nitrogen, etc.
(2) Micronutrients: These are also called trace elements and are required in very small amounts.
for example:- iron, manganese, copper, molybdenum, etc.
Criteria for essentiality of elements:-
(i) The elements are considered to be necessary for supporting the growth, development and reproduction in plants. In the absence of the elements, the plants are not able to compute their life cycle or sets their seeds.
(ii) Each element is specific in their functions, thus cannot be replaced by another element.
(iii) Element must play a direct role in the metabolism of the plant.
Page No 67:
Question 4:
With the help of examples describe the classification of essential elements based on the function they perform.
Answer:
Essential elements can be categorised into four groups on the basis of the various functions:-
(i) Structural Elements: They are the components of biomolecules and are the structural elements of the cells. For example:-
Carbon, Hydrogen, Oxygen and Nitrogen.
(ii) Energy Related Elements: They are the components of energy-related chemical compounds in plants. For example:- Magnesium in chlorophyll and Phosphorus in ATP.
(iii) Catalytic Enzyme: They activate or inhibit the activity of enzymes. For example:- Magnesium (Mg2+) acts as an activator for two enzymes ribulose bisphosphate carboxylase oxygenase and phosphoenol puruvate carboxylase. Both the enzymes are involved in the process of photosynthetic carbon fixation. Zinc (Zn2+) acts an activator for enzyme alcohol dehydrogenase. Molybdenum (Mo) of nitrogenase during the process of nitrogen metabolism.
(iv) Elements altering osmotic potential: Some elements alter the osmotic potential of a cell. For example:- Potassium plays an important role in the opening and closing of stomata.
Page No 67:
Question 5:
We know that plants require nutrients. If we supply these in excess, will it be beneficial to the plants? If yes, how/ If no, why?
Answer:
Micronutrients are some essential nutrients required in trace amount by plants and the slight increase in the concentration than moderate causes toxicity. Any mineral ion concentration present in tissues that reduces the dry weight of tissues by about 10% is considered as toxic. For example:- Manganese toxicity results in the appearance of brown spots that are surrounded by the chlorotic veins. This also competes with iron and magnesium for uptake. Hence, it is concluded that the excessive supply of nutrients is not beneficial for the growth and development of plants.
Page No 67:
Question 6:
Trace the events starting from the coming in contact of Rhizobium to a leguminous root till nodule formation. Add a note on importance of leg haemoglobin.
Answer:
Events involved in the formation of nodule by multiple interactions between Rhizobium and roots of the host plant are as follows:-
(i) The Rhizobia multiply and colonise the surroundings of roots. They get attached to the epidermal and root hair cells.
(ii) The root hair curls and then the Rhizobium invade the root-hair.
(iii) An infection thread is produced that carries the bacteria into the cortex of the root and here they initiate the process of nodule formation in the cortex of root.
(iv) Then the bacteria are released from the thread into the cells that led to the differentiation of specialised nitrogen fixing cells.
(v) Nodule is formed and establishes a direct vascular connection with the host for nutrient exchange. Leghaemoglobin is a red-coloured iron containing pigment present in the root nodules of leguminous plants. They act as an oxygen scavanger for nitrogenase enzyme plays
an important role in nitrogen fixation.
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Question 7:
Give the biochemical events occurring in the root nodule of a pulse plant. What is the end product? What is its fate?
Answer:
Nitrogenase enzyme and leghaemoglobin is present in the root nodules that carry out all the required biochemical components. Nitrogenase enzyme is a Mo-Fe protein. It catalyses the conversion of atmospheric nitrogen into ammonia. Ammonia (NH3) is the first stable product of nitrogen fixation. The chemical reaction involves:-
Fate of Ammonia:-
The ammonia formed is protonated to form ammonium ions at physiological pH.
Many plants can assimilate nitrate and ammonium ions but ammonium ion is toxic and cannot accumulate in plants. The ammonium ions are used for the synthesise of amino acid glutamate by the process of reductive amination and it further form other aminoacids through transamination.
Page No 67:
Question 8:
Hydroponics have been shown to be a successful technique for growing of plants. Yet most of the crops are still grown on land. Why?
Answer:
Hydroponics is the technique of growing plants in a nutrient solution. It is used for the commercial production of vegetables such as tomato, seedless cucumber and lettuce. But still many plants are still grown on land because:-
(a) Plants that can be grown by this technique need repeated supply of nutrients and air. This is highly difficult.
(b) This technique is highly expensive and such plants are not commercially viable.
(c) Plants can become highly susceptible to environmental conditions because they are grown in laboratory conditions.
(d) Plants require high level of sterlization and maintenance while growing through this technique.
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